1. Field of the Invention
This invention relates to pumping units in the oil field and more particularly, to a hydraulic pump unit which is characterized by great efficiency of operation and achievement of optimum well maintenance in pumping oil from oil bearing strata. The hydraulic pump unit of this invention includes a support frame which is slidably mounted on a push-off tray and can be displaced away from the well head by a hydraulic cylinder in order to perform necessary maintenance on the well. The unit effects pumping of oil from the well by means of a pair of hydraulic cylinders attached to a traveling head assembly which carries a pair of rollers and a pair of matching chains mounted on the rollers and attached to the polish rod by means of a bridle. The hydraulic cylinders operate to lift the polish rod by moving the head assembly upward and causing the chains to traverse the rollers. The hydraulic pump unit of this invention is rugged, yet efficient, and is easily installed and removed from the well site.
2. Description of the Prior Art
Pumping units used to pump oil from oil-bearing strata or intervals in the oil field have been known for years. Such pumping units are typically characterized by a drive means or motive force such as an electric motor or diesel engine which cooperates with the drive pulley of single, double and triple reduction gear units to effect pivotal motion of a generally horizontally-disposed walking beam and a horsehead. This movement of the horsehead and walking beam in turn causes a wire-line bridle attached to a string of sucker rods located in the well to reciprocate and pump oil from the strata. The gear box typically carries a pair of cranks and cooperating pistons which are pivotally attached to the walking beam and cause the walking beam horsehead to reciprocate at a selected rate. Conventional pumping units and particularly, conventional gear-reducing units provided in pumping units for transmission of primary drive power to the pitmans and the walking beam at a controlled rate are relatively complex devices generally characterized by multiple gears in an enclosed housing and partially immersed in a pool of oil for lubrication. As long as the oil is maintained at the proper level within the housing the slow speed gear of the gear reducing units is partially immersed in the oil and receives and disburses continuous lubrication. In most cases the lubricating oil composition in the gear reducing unit must be carefully prescribed for any given installation. In any case the lubricating oil level must be maintained above the low mark in the oil-indicating gage, but should not be filled above the high mark. Furthermore, at least every six months the operator must collect a sample of the oil and check it for possible dirt, sludge, water emulsion or other forms of contamination. Due to the complexity of the commonly used herringbone gear units, if a gear breaks or the unit fails for other reasons, such as lack of sufficient lubricating oil or oil of a particular composition, the pumping unit is rendered inoperative until the gear reducing unit is replaced or the defective part is replaced in the unit. Furthermore, both the high speed and the low speed gears in conventional gear reducers, as well as other parts in these units are quite expensive and add significantly to the cost of maintaining and operating the pumping units over a period of time. Failure of gears and gear reducing units is quite common due to the lack of resistance to shock and the large load applied to the engaged teeth.
Other pumping units known in the prior art and used in the oil field include units which are driven by hydraulic cylinders instead of the motor driven gear box type unit described above. These units are designed to eliminate the high cost of operation inherent in the gear box machines, and in many instances are superior to such conventional installations using these gear systems.
Accordingly, it is an object of this invention to provide a hydraulic pump unit which is characterized by great efficiency and utility and which includes a slidably mounted support frame which permits the pump unit to be moved temporarily away from the well head during periods of maintenance on the well.
Another object of this invention is to provide a new and improved hydraulic pump unit which is characterized by a pair of hydraulic cylinders for lifting a slidably-mounted head assembly which utilizes a pair of rotatably-mounted chains to lift the polish rod, sucker rods and pump responsive to operation of the cylinders in order to pump oil from the well.
Still another object of the invention is to provide an improved pumping unit of the hydraulic cylinder design which includes a movable support frame; a stationary mast mounted on the support frame and slidably receiving a traveling mast; a pair of rotating wheels mounted on the traveling mast and fitted with a pair of chains having one end connected to the stationary mast and the opposite end to a bridle which carries the polish rod for pumping oil in the well; and further including a pair of hydraulic cylinders operable to periodically extend the traveling mast on the stationary mast and lift the polish rod as the chains rotate on the rollers, to pump oil from the well.
A still further object of the invention is to provide a new and improved hydraulic pump unit for pumping oil from oil-bearing strata in a well, which pump unit includes a support frame slidably mounted on a cooperating push-off tray whereby the frame and pumping unit can be displaced on the tray to allow access to the well head for maintaining the well; a stationary mast vertically mounted on the support frame and slidably carrying a traveling mast; a head assembly mounted on the traveling mast and characterized by a pair of rotatably-mounted rollers carrying chains, the chains each having one end connected to the stationary mast and the opposite end attached to a bridle supporting a polish rod which extends into the well; and a pair of hydraulic cylinders cooperating with the head assembly whereby extension of the pistons in the hydraulic cylinders lifts the head assembly and the traveling mast and causes the chains to traverse the rollers to lift the polish rod and the attached sucker rod string and well pump, and pump oil from the well.
Still another object of the invention is to provide a simple, yet rugged and dependable hydraulic pump unit for pumping oil from oil-bearing strata in an oil well which combines the simplicity of dual hydraulic cylinder operation with the dependability of a chain and roller-operated sucker rod string and the feature of displacing the supporting frame and pump unit on a stationary carrying tray to maintain the well.